This invention relates to a special solvent column for gel-permeation chromatography useful for measuring molecular-weight distributions of organic materials, the molecular-weight distributions of which have been impossible in gel-permeation chromatography (hereinafter referred to as "GPC") using as an eluent tetrahydrofuran or chloroform usually used and a GPC method using said special solvent column.
It is an important thing to measure molecular-weight distributions of high polymers and organic oligomers rapidly in developing excellent organic materials and conducting careful quality control. In order to respond to such a requirement, the GPC method has been developed and applied widely as a comparatively simple method for measuring molecular-weight distributions. The GPC is an analyzing method as described in, for example, J. C. Moore: J. Polym. Sci., A2, 835 (1964), using a tube made of stainless steel, etc., packed with porous styrene-divinylbenzene copolymer spherical particles (packing material) as a major constituent (gel-permeation column) and comprising the steps of dissolving a sample to be analyzed (solute molecules) in a moving phase solvent (eluent), introducing the sample solution into the column by using a constant flow pump from an inlet so as to pass through the column to an exit while developing, fractionating the sample depending on molecular sizes from larger ones to smaller ones in relation to pore sizes of the packing material, and measuring separation of the moving phase against the elution volume and the amount of the solute molecule flowed out by using a suitable detector. Therefore, in order to conduct rapid and precise measurement of molecular-weight distributions by the GPC method, the quality of the column packed with a packing material is very important.
Further, even if porous styrene-divinylbenzene copolymer spherical particles mentioned above are used as a packing material, there often takes place reversion of separation of the solute molecules and the effluent order depending on the kind of the moving phase solvent. This can be seen when a polar solvent having a large solubility parameter such as methanol or water is used as the moving phase solvent.
Thus, there is a limitation to solvents usable for measuring molecular-weight distributions effectively by using the GPC method and it is recommended to use a column packed with a packing material sufficiently immersed in the same solvent as used for flowing. As the solvent, tetrahydrofuran (THF) and chloroform (CHCl.sub.3) are generally used. But some samples are not soluble in THF or CHCl.sub.3 and it is not possible to measure these samples at normal temperatures. Examples of such samples are polyethylene terephthalate (PET), PET oligomers, polyesterimides, and the like. As a method for measuring such a hardly soluble sample, there is employed a GPC method carried out at a high temperature (about 80.degree. to 140.degree. C.) considering the fact that such a sample is soluble in hot cresol type solvent. But since the measurement is carried out at such a high temperature, there are many problems in that a true molecular-weight distribution of the sample can hardly be obtained due to hydrolysis and the like of the sample, operation of the GPC apparatus is not easy and lacks in safety, reproducibility of data is not so good, and the like.
Therefore, extensive studies have been made on solvents which can sufficiently dissolve a sample at normal temperatures and have a molecular-weight distribution measuring effect against porous styrene-divinylbenzene copolymer spherical particles and thus this invention has been accomplished.